1. Field of the Invention
The present invention relates to a junk mail rejection system for rejecting junk mail in electronic mail.
2. Description of the Related Art
Recently, as various networks such as Internet, etc. have been developed and wireless terminal equipment has made remarkable progress, more and more information has been transmitted and received by electronic mail, and a number of users utilize electronic mail personally and for business.
On the other hand, with an increasing utilization factor of electronic mail, there arises the social problem that the amount of electronic mail from an undesired source, that is, junk mail, has largely increased. Now, an Internet service system using a wireless telephone as an example is explained. There is a center capable of gaining access through a network such as Internet, etc., and an electronic mail address is assigned to a wireless telephone of a subscriber. When electronic mail is transmitted to the electronic mail address of a subscriber, the information about the electronic mail is transmitted from the center to the wireless telephone of the subscriber if the electronic mail is transmitted through the center and the wireless telephone of the corresponding subscriber is set ON. If the electronic mail address of the subscriber is correctly specified as a destination, then electronic mail is received by the wireless telephone regardless of the intention of the subscriber to receive the mail, thereby generating junk mail. Especially when the service fee is charged to a receiving subscriber depending on the amount of information received by the subscriber from the center in the system of the Internet service, the total amount of payment of the subscriber who receives junk mail increases due to the junk mail, thereby causing the subscriber to suffer a loss. One of the solving methods is to change the system into a system in which a fee is charged to a transmitter's account, or into a system in which for each piece of electronic mail, a subscriber can select whether or not the electronic mail is to be received. However, it means to largely change an entire system, and requires a high cost. Other than changing the system, there is a method of avoiding a charge to a receiver when the amount of information is equal to or smaller than a predetermined amount. However, this method cannot completely avoid a loss by junk mail having a large amount of information. Furthermore, there can also be a method of changing the electronic mail address of a subscriber, but changing an electronic mail address requires notifying all possible transmitters of desired electronic mail of the change of the electronic mail address, thereby imposing a heavy load on the subscriber. Otherwise, there can be an existing system in which a center includes means for performing capabilities of: ‘specified reception’ for receiving only mail whose source is specified source electronic mail address; ‘specified rejection’ for rejecting only mail whose source is specified source electronic mail address; ‘batch rejection’ for rejecting reception of all electronic mail, etc. However, the ‘specified reception’ is restricted in the number of electronic mail addresses to be specified, and electronic mail to be received cannot be received if it is not specified. Similarly, since reception of all electronic mail is rejected in the ‘batch rejection’, electronic mail to be received cannot be received. Additionally, since a source electronic mail address of junk mail can be constantly changed, the junk mail cannot be effectively avoided in the ‘specified rejection’.
Another problem with the junk mail is that old necessary electronic mail is removed by a large amount of junk mail received when there is a restriction in the number of pieces of electronic mail to be stored for each subscriber and the predetermined number of pieces of later electronic mail is stored.
Furthermore, malicious electronic mail can be acts of terrorism of damaging the function of mail at the destination by intentionally concentrating a large amount of junk mail. The acts of terrorism not only aims at a person but also aims at an organization such as a large company, government and municipal offices, etc. whose domain names are often published, and the user name in the electronic mail address of each member can be simply the name of the member and the pattern of the address is simple. Therefore, a terrorist can easily transmit electronic mail to the electronic mail address of a member of an organization. Furthermore, if each member suffers the acts of terrorism when the electronic mail received by a server of the organization is set to be transferred to his or her own wireless telephone, then old but necessary electronic mail are all cleared as described above. Additionally, it requires a cost of using a telephone line to delete a large amount of unnecessary mail, thereby badly damaging the subscriber.
Whereas junk mail causes the above mentioned damage, some electronic mail belonging to normal junk mail to be transmitted at random to a number of general subscribers does not function as junk mail depending on the type of receiving subscriber. That is, although electronic mail functions as junk mail for some subscribers, it is not junk mail if the contents of the mail are desired by other subscribers. Namely, such mail has a possibility of creating an mail distribution industry more effective than conventional direct mail distributed by conventional mail.